Fuse.



L. W. DOWNES & H. C. PATTON.

FUSE.

APPLICATION FILED FEB. 26, I9l.

Patented Nov. 27, 1917.

2 SHEETS-SHEET I.

L. W. DOWNES L R. C. PATTON.

FUSE.

APPLICATION FILED FEB. 26. |917.

1 ,248,090. Patented Nov. 27', 1917'.

2 SHEETS--SHEET 2.

WW# m www UNITED sTATEs PATENT oinrwE` LOUIS W. DOWNES AND RALPH CLIFTON PATTON, 0F PROVIDENCE, RHODE ISLAND,

ASSIGNORS TO D W 'FUSE COMPANY, OF PROVIDENCE, RHODE ISLAND, A CORPO- RATION OF RHODE ISLAND.

FUSE.

Speoication of Letters Patent.

Patented Nov. `2'7. 1917.

Application illed February 26, 1917. Serial No. 150,873.

To all whom it may omwem.' 1

Be it known that we, Louis W. DoWNES and RALPH CLIFTON PATTON, citizens of the United States, and residents of the city of Providence, in the county of Providence and State of (Rhode Island, have invented cer- -tain new and useful Improvements in Fuses, of which the following is a specification.

p rlhis invention relates to electric fuses of the class adapted to be connected in an elecV tric circuit to open ity when an overload or short circuit occurs, and the object of this invention is to provide a compound fuse of that type in which two or more fusible elements are connected together, the elements being constructed in such a way that but one will fuse at a time.

A further object of this invention is to provide a main fusible link or element of a given ampere capacity, and an auxlliary link of a greater resistance, part of the latter bein wound into a coil, preferably of helical orm, whereby an excessive current iiow first opens the main link and, is then automatically shunted through the auxiliary link of coil form which opens soon after. By this construction a fuse of high voltage and' current rating can be made to operate quietly and without violence even when an excessive current is passed therethrough.

A still further object of this invention is to provide a main fusible link connected electrically in parallel with an auxiliary link, the main link being surrounded by a liquid arc suppressing material, and that portion of the auxiliary link which is intended to fuse being surrounded by a permeable granular or fibrous arc suppressing substance soaked withthe arc suppressing liquid.

A still further object of this invention is to provide a main fusible link connected electrically in parallel with an auxiliary fusible link, the main link being attached to spring terminal strips under tension so that when a portion of the main link melts, the remainin stubs of the link are quickly moved apart y said tension so as to aid in breaking the electric arc between the main link stubs, the movement of the spring terminal strips being the same as described in Patent No. 1,203,316, issued Oct. 31, 1916.

It is found in practice that when fuse links of the non-helical or strai httype not under mechanical tension are ca led upon to interrupt greatly excessive currents at high voltages, much of the link is instantaneously converted into vapor, frequently in a violent and explosive manner. But when a properly roportioned compound link, con sisting o a main link under mechanical tension tending to separate its ends, and an auxiliary link of greater resistance connect* ed electrically in parallel with it, both the main and auxiliary links being immersed in liquid arc suppressing material, and that portion of the auxiliary link which is intended to fuse being coiled and surrounded also by a permeable granular or fibrous arc suppressing substance, is caused to open a greatly excessive current at hi h voltage, the rupture of the current is e ected with great ease and with practically no disturbance. The quiet operation of this form of compound link is due to the following sequence of phenomena:

When the excessive current traverses the fuse,'the -main link melts first because it carries a greater proportion of the total current than does the auxiliary link of higher resistance, and also because the auxil` iary link when properly designed usually has a higher melting point than does the main link. As soon as the middle portion 0f the main link is destroyed, the spring terminal strips separate the remaining stubs of the link very rapidly so that a large gap is immediately formed to interrupt the current. As soon as the passage of current through the main link is stopped, the current is forced to flow through the auxiliary link alone. Since the auxiliary link or circuit has a much greater resistance than the two links in parallel had, and because the yauxiliary link s shape is that of a choke coil,

the current is materially reduced, being partially restrained by the high resistance and the choking action of the coiled portion. The flow of current through the auxiliary link is still further reduced because of the increasing resistance of this' link brought about by its rapid rise in" temperature. When the auxiliary link reaches its melting point, some part of itscoiled portion fuses,

thus stopping even the restricted current ilow which traverses this circuit after the main link blows. y

When the main link melts, it does so without violence as it is not re uired to entirely interrupt the current ow, but merely to shunt it through a somewhat more difiicult ath. When the auxiliary link fuses or blows, the ruptureof the current is effected without violence because the current has been reduced to small value before this ha pens, and also because the rupture takes p ace in the presence of suitable liquid and permeable granular or fibrous arc suppressing materials. v

An essential feature of our improved type of compound fuse is that an auxiliary llnk, a portion of which is coiled and surrounded b both liquid and permeable granular or fibrous arc suppressing materials, is mounted to operate in combination with a main link held in tension by spring terminal strips, the auxiliary link being of greater resistance than the other. Thereby the opening of the link of less resistance shunts the current into the link of greater resistance and both links blow quietly, owing to the rapid breaking of the arc at lthe main link,

and the presence of proper arc quenching materials about each link. Thus the combination of the two links operate quietly and safely by breaking the current in successive stepsinstead of all at once.

It has been found by experiment that when the coiled portion of the auxiliary link is surrounded by the liquid arc suppressing material only, the blowing of the link may be accompanied by considerable violence as the arc suppressing liquidbecomes heated sufficiently to be partly transformed into gas, which we find to be undesirable. By surrounding the coiled portions of the auxiliary fibrous arc'suppressing material and the arc suppressing liquid. y t has been observed that the coiled portions of the auxiliary link when surrounded by thecombined arc extinguishing materials in this way have a tendl ency to rupture at a number of separated points, whereas, a coiled link not so sur- .One type of such fuse is casing or casings.l

.being a receptacle 14 which is filled with a 105 rounded usually fuses at only one point. Thus it is seen that the coiled portion of the auxiliary link acts much more positively in opening the circuit when surrounded by the combined arc su pressin materials than when surrounde b t e liquid alone. Therefore, the permea le granular or fibrous arc suppressin material and the liquid arc suppressingsu stance coperate to produce the proper arc quenching effect when placed irolpnd the coiled portions of the auxiliary With these and other objects in view, the invention consists of certain novel features of construction, which will be more fully described and particularly pointed out in the appended claims.

In the accompanying drawings:

Figure l-is a longitudinal section showing a compound link immersed in liquid arc suppressing material, supported in one form of suitable container.

Fig. Qf-is a side elevation showing the compound fusible link attached to terminal blocks as it appears before being blown by an excessive current, and showing the aux 90 iliary link casing in section.

Fig. 3-is the' same as Fig. 2 but showing both of the links as having been blown by an .abnormal flow of current.

A It is found in practice that 'a liquid arc`95 suppressing material such as certain kinds of oil may be used to great advantage, particularly in fuses of very hi hvoltage rating. illustrated in Fig.

1 in which two helical fuse links 10 are con- 100 nected to work in combination with a fiat link 13. These compound formsof fuses may be arranged to operate in any stylewof That shown 1n Fig. 1

liquid arc suppressing material and in which is mounted the main link 13 supported from the terminal blocks 15 by the spring terminal stri s 16. f

The tu ular casings 17 are preferably 1m filled with a suitable granular or fibrous or otherwise porous or intersticed arc suppressing matenal in which they areimmersed,

which liquid enters the casings 17 through 115 the openings 18 therein.

It 1s found in practice that when this auxiliary coil is surrounded by such a combination of arc suppressing materials that its ac- ,tion is much more positive and effective and that the fuse blows much more quietly than when surrounded by either the liquid or the porous material. alone.

The operation of this form of fuse when carrying a current is as follows The current enters throu h'the terminal conductor 125 19, passes throug the contact strip 20, the terminal block 15, and into the upper end of thepspring strip 16. The current thereupon divides, the most of it traveling down through the remainder of the spring strip 16, across the fusible element 13 and up through the other spring strip 16. The smaller remaining portion of the divided current traverses the coils and the wire 21. The two components of the current reunite before entering the other terminal block 15, and the whole current then passes out through the remaining terminal conductor 23.

The separate coils 10 which are connected by the wire 21, shunt a small portion of the total current because these coils are joined at their upper ends to the spring strlps 16 by means of the clips 22. lVhen a fuse is constructed with a main link of the fiat type and an auxiliary link of the helical type, and an overload or short circuit occurs on the line, the main strip is melted at once and the current is shunted through the helix of greater resistance and reactance. This shunting action reduces the potential across the terminals of the main fusible strip and thus greatly reduces the violence of the arc at that point.

As the helical link contains a relatively large amount of metal and as its melting point is usually higher than the main link, it has a relatively greater heat storage capacity. Therefore the time required to heat it to its melting point is somewhat greater than the time required to fuse the main link. This effect renders the operation of the coil a little more sluggish than the straight or non-helical forms, and allows an inductive circuit to be opened without undue potential fluctuations and surges which' would ensue with any very quick opening link. 40 These voltage rises and surges are often injurious to the general insulation of the system and therefore the slightly retarded nterruption of the current flow in the coil link accomplishes the rupture of the current in a most advantageous way by reducing these surges. During the brief interval elapsing between the blowing of the main link and the auxiliary coil link, the current rise is impeded and held partially in check by the counter electromotive force developed in the helix and by its relatively high resistance. This counterA electromotive force is due to the coil shape of the conductor which forms the auxiliary link. The coil link has a typically inductive shape which possesses the well-known characteristic of developing counter electromotive force to oppose the potential tending to send a rising current through it. It is, therefore, A' seen that inasmuch as the main link melts while shunted by the helix it operates quietly, and that the coil link melts an instant later While the current is restrained,

thus the opening of the circuit is accomplished without undue voltage fluctuations and without disturbance.

ille have shown and described one illustrative embodiment of our invention, but we desire it to be understood that the details of construction may be varied without depart-ing from the spirit of the invention, the scope of which is defined and limited only by the appended claims.

e claim:

1. An elect-ric fuse comprising a fuse link,

a. casing for said link, and an intersticed arc suppressing filling in said casing saturated with a liquid arc suppressing material. 2. An electric fuse comprising a fuse link formed in a helical coil, a casing for said coil, and a filling of intersticed arc suppressing material saturated With a liquid arc suppressing material in said casing about said coil.

3. A compound electric fuse comprising a main link, andan auxiliary link, said main link being inclosed in a main receptacle and surrounded by a liquid arc suppressing material, and said auxiliary link being mounted in an auxiliary casing within the main casing.

4. A compound electric fuse comprising a main link and an auxiliary link, said main link being inclosed in a main receptacle and surrounded by a liquid arc suppressing ma- 'terial and said auxiliary link being mounted in an auxiliary casing within said main casing, said auxiliary casing containing an intersticed arc suppressing material.

5. An electric fuse comprising a main link and an auxiliary link, said main link being inclosed in a main receptacle and surrounded by a liquid are suppressing material and said auxiliary link being mounted in an auxiliary casing within the main casing, and means in said auxiliary casing for admitting the liquid from the main casing.

6. An electric fuse comprising a main link and au auxiliary link, said main link being inclosed in a main receptacle and surrounded by a liquid arc suppressing material and said auxiliary link being mounted in an auxiliary casing withinthe main casing and containing an iutersticed arc suppressing material, and means in said auxiliary casing for admitting the liquid from the main casing whereby the filling therein becolnes saturated with said liquid.

7. A compound fuse comprising a main link, an auxiliary link of helical form connected in parallel with said main link, a casing for said auxiliary link having a filling of intersticed arc suppressing material, and a casing inclosing both of said links and containing` a liquid arc suppressing material in which said links are submerged.

8. A compound fuse comprising a. main link, an auxiliary link connected in parallel with said main link, a casing for said auxiliary link having a filling of intersticed are suppressing material, a, casing inclosing both of said links and 'containing a liquid are suppressing material in which said links are submerged, and means for automatically operatlng the fused members of the main link after blowing.

LOUIS w. DOWNES. RALPH CLIFTON PATTON.

Witnesses:

GEORGE W. STEERE, H. F. MACGUYER. 

